How Is Energy Expended When Holding a Bucket Stationary?

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Discussion Overview

The discussion revolves around the concept of energy expenditure when holding a bucket stationary, particularly focusing on the physiological aspects of muscle function and the mechanics of work in physics. It explores the relationship between force, distance, and energy in the context of human muscle activity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that while holding a bucket stationary involves no displacement (W = Fx0 = 0), they feel fatigued and are expending energy, raising questions about the nature of work in this context.
  • Another participant explains that energy is expended due to the inefficiency of the human body, as muscles contract repeatedly and dissipate energy as heat, suggesting that perfect steadiness is unattainable.
  • A participant questions whether the work equation could apply if considering the movement of muscle fibers, indicating a potential for calculation despite the impracticality.
  • Another participant expresses uncertainty about applying a work equation to muscle fibers, indicating a gap in understanding.
  • One participant introduces the concept of elastic energy, hinting at a connection to muscle mechanics.
  • A later reply discusses the molecular level of muscle contraction, mentioning actin and myosin interactions and ATP usage, suggesting a deeper understanding of energy expenditure in muscle activity.

Areas of Agreement / Disagreement

Participants generally agree that energy is expended when holding a bucket stationary, but there is no consensus on how to quantify this energy expenditure or apply traditional work equations to muscle activity.

Contextual Notes

There are limitations in the discussion regarding the assumptions about muscle efficiency, the definitions of work in physics versus biological contexts, and the unresolved application of equations to muscle mechanics.

Who May Find This Useful

This discussion may be useful for individuals interested in biomechanics, physiology, and the interplay between physics and human muscle function.

houlahound
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I know this will involve a simple answer but I just can't get it atm.

work = force X distance and has units of Joules ie energy

when I hold a bucket of water elevated so arm is parallel to the ground I have done some work.

I now hold it out there and my arm muscle burns and fatigues fighting gravity ie I am metabolising energy to hold the bucket yet the bucket has moved no distance hence W = Fx0 =0 but I am definitely expending energy?
 
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You are expending energy because the human body is an imperfect machine. The energy is spent contracting you muscles fibers over and over again and is eventually dissipated as heat. That's how your muscles work and why it is impossible to hold something perfectly steady. If you replaced your arm with a metal bar, then no energy would be expended.
 
so W=FxD still holds if you calculated the movement of the muscles?

I am not suggesting anyone would do the calculation but just saying?
 
I believe so, but I don't know how to apply a work equation to a stretching muscle fiber.
 
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elastic energy equation?
 
You would have to go down to the level of the actin and myosin. It uses the energy in ATP to trigger a little "ratchet" movement which exerts a force over a distance on a molecular scale.
 
gotcha
 

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